What Is Mathematics? is a mathematics book written by Richard Courant and Herbert Robbins, published in England by Oxford University Press. It is an introduction to mathematics, intended both for the mathematics student and for the general public.
First published in 1941, it discusses number theory, geometry, topology and calculus. A second edition was published in 1996 with an additional chapter on recent progress in mathematics, written by Ian Stewart. A Spanish translation of the second edition, ¿Qué Son Las Matemáticas?, was published in 2002. Millions of copies of unauthorised Russian and Chinese editions have been printed.[1]
Although Robbins wrote most of the book, he received almost none of the royalties. Courant owned the copyright, and passed almost none of the money on to Robbins.[2]
Reviews

^Preston, Richard (2008). Panic in Level 4. USA: Random House. p. 38. ISBN987-1-4000-6490-8. "The book is a classic. Millions of copies of it had been printed in unauthorized Russian and Chinese editions alone."

^Preston, Richard (2008). Panic in Level 4. USA: Random House. p. 38. ISBN987-1-4000-6490-8. "Robbins wrote most of the book, while Courant got ownership of the copyright and collected most of the royalties but paid little of the money to Robbins."